look at the quantum motors on there, they are B-50 sized and in the 1000kv range will run a turbax even, if you stick one in the 4 inch fans it will run on less cells. To save you some hunting you wont need to get a C-50 motor, B-50 is same thing without fins and thats what you need to fit it in all the fans that are out there. And lehner are not ideal big fan motors due to just 2 poles, they dont have as much torque as the 4 pole and up motors that are now available. They were great motors when nothing else could take the voltage but now theres much beter for 1/4 the price. Pending on the size of car your shooting for, another cheap combo is the byron fan with a Hacker A-50 14S 10 pole outrunner, does about 2800 watts with just 69 amps and will give you about 12 pounds of thrust but it is a 6 inch fan.

Barry